Design for Preaching
by H. Grady Davis. By the "Wittgenstein of homiletics," this 1958 book continues to be one of the best books on preaching. No matter how many years you have been preaching, your preaching will improve as you read and think about what Henry Davis has to say.
Homiletic Moves and Structures
by David G. Buttrick. His homiletic is geared toward constructing sermons that people will actually remember after they leave worship. He also spends half of the book on the art of interpreting the biblical text with regards to preaching, arguing that different literary forms demand different types of sermons.